
I haven't read the new raws yet, but in here they haven't really touch the subject of who or how he was, other than saying he reincarnated as his rival's brother and that he hated Cin Nian in the past life for taking his lover (though it was more like he liking the same person that past 'Cin Nian' dated.)

The chapter where he has the nightmare of the dead grandpa and Cin Nian trying to kill him (Sorry forgot the chapter number, but is the chapter or after chapter where Xu Xian sees Cin Nian sitting at the restaurant with ketchup on his face but thought it was he's ghost that he was seeing, that night is where he had the nightmare) following the nightmare he confessed a ghost cannot kill him so he knew he was dreaming and goes into saying about his reincarnation, and why he loathed Cin Nian. Apparently they were love rivals in the past, and seeing on the previous chapter he hinted that 'God gave him a 2nd chance to live so he wasn't going to die in the car accident' just says more to the story.

Yes there is, it is mention that Xu Xian remembers his previous past life and that he just happened to be reincarnated as Cin Nian's younger brother when they were love rivals in the past life. That's why in the previous chapter he says; 'god gave me a 2nd chance to live so I am not going to die like this' (during driving before the car accident)
Who was he bfore the reincarnation thingy and why was he so angry about Ci Nian? Is it just jealousy or some other reasons?